This invention relates to door opening and closing apparatus and particularly to methods and apparatus for improving the operational safety of door opening and closing apparatus.
A garage door operator for opening and closing doors typically includes an electrical motor having an up winding and a down winding. When the up winding is energized by an operating voltage, the motor shaft rotates in one direction to raise the door and when the down winding is energized by the operating voltage, the motor shaft rotates in the opposite direction to lower the door. A control unit responds to external stimuli such as door open and close request signals by energizing the proper winding to serve the request. The actual connection of the operating voltage to the up and down windings is provided by a pair of relays, one associated with each winding, the relays respond to signals from the control unit by connecting the source of operating voltage to their associated windings. The control unit frequently comprises integrated circuit logic which individually operates the relays via relay drivers.
Integrated circuit logic is subject to faults as are relay drivers and relays themselves. Thus, improper relay control signals can be generated by the integrated circuit logic or proper control signals can be inappropriately responded to by the drivers and relays. Although such faulty operation is infrequent, the effects of such are to be avoided, since they can, in extreme situations, cause injury to people in the vicinity of the apparatus.
The problem of faulty operation has been recognized and systems devised to protect individuals from faulty operation. U.S. Pat. No. 4,338,553 to Scott, discloses an apparatus which, when a door limit controlling oscillator fails, generates relay control signals to move a door to the up position. The Scott arrangements checks only the proper oscillator operation, and does not determine proper door operation in response to generated control signals. U. K. Patent Application No. 2 072 884 to Matsuoka, et al., discloses an apparatus which uses timers to check for proper door operation. When a door operation such as opening the door, is not completed within a period of time, e.g., 23 seconds, representing the maximum time for the completion of the operation, the timer signals a fault and remedial action is taken. The remedial action is to remove the driving voltage from both up and down motor windings by means of a first relay and to energize the up winding by means of a second relay. Importantly, no fault will be sensed by the disclosed arrangement until a door movement should b completed, e.g., 23 seconds, by which time injury may have occurred. Also importantly, the additional relays and circuitry required for the response to faulty door operation are not normally exercised so that faults within them will remain untested and the additional relays and circuitry add to the expense and complexity of the apparatus.
Known fault protection systems for garage door operators do not detect inappropriate door movement rapidly enough, are not tested by normal operation, and add unncessarily to the expense and complexity of the overall apparatus.
The present invention solves the problems of prior systems by rapidly sensing inappropriate door movement and terminating such inappropriate movement using a minimum amount of additional circuitry, which is routinely exercised to protect against latent faults. The apparatus of the present invention includes circuitry for sensing the rotation of the door driving motor shaft and checking such rotation after issuing door operating commands. When the measured rotation is not appropriate for the last door operating command, fault control signals are generated. The door controlling circuitry of the apparatus includes three (3) door controlling switch arrangements for selectively energizing the up and down motor windings of the door driving motor. A control unit operates in cooperation with the motor shaft rotation sensor to detect improper door movement and to control the switching circuits to stop and move the door up. Upward movement of the door is assured when faced with any single fault in the door control circuitry.
An apparatus for opening and closing a garage door in accordance with the present invention comprises a motor with a rotatable member for rotating in a first direction to open the garage door and in a second direction to close the garage door, and motor control circuitry responsive to control commands for selectively connecting electrical power to the motor to cause rotation of the rotatable member. A control arrangement, shown in the embodiment as a logic unit, responds to external stimuli by selectively sending control commands specifying rotation of the rotatable member in the first direction, rotation of the rotatable member in the second direction or no rotation by the rotatable member. After predetermined control commands, the actual rotation of the rotatable member is sensed and when actual sensed rotation is not in accordance with the last control command, fault control signals are sent to the motor control circuitry. The fault control signals can be used to cause the motor to raise the door to its safe upper limit.
Advantageously, the motor control circuitry comprises a plurality of relays which cooperate to provide safe operation of the door when faults occur within the motor control circuitry. In the preferred embodiment, the motor includes up and down windings for controlling the two directions of rotatable member rotation. The motor control circuitry includes a first relay which responds to control commands by connecting electrical power to either the up motor winding or to an intermediate conductor. A second relay responds to control commands by selectively connecting the intermediate conductor from the first relay to the down winding, and a third relay responds to control commands by connecting electrical power to the up winding. By this interconnection of relays, door movement can always be stopped and in most situations, it will be stopped in the upmost door position.
The logic unit of the embodiment responds to the external stimuli by generating upward movement control commands, downward movement control commands and door stop commands. When the door movement after a command is not in accordance with the command, the logic unit generates fault control signals which cause upward movement of the door.